class_docstr: Interface for implementing a Trial Scheduler class.
  
  Note to Tune developers: If a new scheduler is added, please update
  `air/_internal/usage.py`.
code: def __init__(self):
      tag_scheduler(self)
  
imports: from typing import Dict, Optional, TYPE_CHECKING
  from ray.air._internal.usage import tag_scheduler
  from ray.tune.result import DEFAULT_METRIC
  from ray.tune.experiment import Trial
  from ray.util.annotations import DeveloperAPI, PublicAPI
label_desc: Use image node_id 1 to create a new TrialScheduler object  with example: obj = TrialScheduler()